Because they're such versatile pieces of clothing (belt, shawl, scarf, mask, and like 8 types of hat) they're extremely common all over the middle east by different names. Basically any time you see an arab with some sort of cloth covering their head or neck it's going to be a keffiyeh (or shemagh, or ghutra (?), or whatever they're locally called).

Early zionist Jews that emmigrated to Palestine when it was under Ottoman and British control made an actual effort to integrate with the locals and started wearing keffiyahs too, so they still get used by Israelis even though they're not as popular as they were.